Most major cruise lines offer Mexican Riviera cruises for at least part of the year, with large ships sailing from San Diego, Los Angeles, and San Francisco. Popular with travelers from western states who don't want to fly cross-country, these cruises visit such Mexican ports as Acapulco, Mazatlán, Puerto Vallarta, and Cabo San Lucas. However, in summer months, when most cruise lines reposition west- coast-based ships to Alaska, only Carnival and Royal Caribbean continue sailing short "Baja Mexico" cruises that call at Catalina Island and Ensenada, Mexico year-round.